1. Field of the Invention
The present invention relates to bioassays, and more particularly, to the use of metallized surfaces to enhance intensity of chemiluminescence species or reactions in assays thereby increasing sensitivity and detectability of same.
2. Background of the Related Art
The use of light-producing chemical reactions for quantitative detection in biotechnology is increasing [1-7], especially with regard to chemiluminescence based ligand-binding assays [1-7]. The attractiveness of chemiluminescence as an analytical tool lies primarily in the simplicity of detection [8]; the fact that most samples have no unwanted background luminescence, as is typically observed in fluorescence-based assays [9]; and the fact that no optical filters are required to separate the excitation wavelengths and scatter [8], as is also required for fluorescence-based detection [9].
However, chemiluminescent based detection is currently limited by the availability of chemiluminescent probes, which is not a factor governing fluorescence based detection [9]. Both fluorescence and chemiluminescence based technologies do however suffer from an inherent need for increased sensitivity/detection limits [8, 9]. For fluorescence, this is governed by the quantum yield of the tagging fluorophore, the level of unwanted background fluorescence and the photostability of the fluorophore [9], where as for chemiluminescence, detection is limited by the quantum efficiency of the chemiluminescence reaction or probe, and the time before depletion of the reactants [8]. For both detection systems, an increased luminescence yield would clearly benefit overall detectability and therefore for bioassays, the sensitivity towards a particular analyte.
Recent developments have provided new technology to enhance fluorescence and that can increase the system quantum yield [10-13], the photostability of the fluorophore [10-13] and by using spatially localized excitation can readily remove unwanted background fluorescence [14]. Specifically, techniques such as Metal-Enhanced Fluorescence (MEF) [10-20] also called Radiative Decay Engineering [21] and Surface Enhanced fluorescence (SEF) [22], have used nanosecond decay time fluorophores in close proximity to a variety of different sized [15] and shape [16,17] noble metal nanostructures to overcome the shortcomings of fluorescence technique.
However, to date no one has found any comparable systems to overcome the shortcomings of using chemiluminescent based reaction detection methods.